[PATCH 2/3] drm/i915: Introduce guard pages to i915_vma
From: Chris Wilson Introduce the concept of padding the i915_vma with guard pages before and after. The major consequence is that all ordinary uses of i915_vma must use i915_vma_offset/i915_vma_size and not i915_vma.node.start/size directly, as the drm_mm_node will include the guard pages that surround our object. The biggest connundrum is how exactly to mix requesting a fixed address with guard pages, particularly through the existing uABI. The user does not know about guard pages, so such must be transparent to the user, and so the execobj.offset must be that of the object itself excluding the guard. So a PIN_OFFSET_FIXED must then be exclusive of the guard pages. The caveat is that some placements will be impossible with guard pages, as wrap arounds need to be avoided, and the vma itself will require a larger node. We must not report EINVAL but ENOSPC as these are unavailable locations within the GTT rather than conflicting user requirements. In the next patch, we start using guard pages for scanout objects. While these are limited to GGTT vma, on a few platforms these vma (or at least an alias of the vma) is shared with userspace, so we may leak the existence of such guards if we are not careful to ensure that the execobj.offset is transparent and excludes the guards. (On such platforms like ivb, without full-ppgtt, userspace has to use relocations so the presence of more untouchable regions within its GTT such be of no further issue.) Signed-off-by: Chris Wilson Signed-off-by: Tejas Upadhyay Signed-off-by: Tvrtko Ursulin Signed-off-by: Andi Shyti --- drivers/gpu/drm/i915/gt/intel_ggtt.c | 14 drivers/gpu/drm/i915/i915_gem_gtt.h | 3 ++- drivers/gpu/drm/i915/i915_vma.c | 27 ++-- drivers/gpu/drm/i915/i915_vma.h | 5 +++-- drivers/gpu/drm/i915/i915_vma_resource.c | 4 ++-- drivers/gpu/drm/i915/i915_vma_resource.h | 7 +- drivers/gpu/drm/i915/i915_vma_types.h| 3 ++- 7 files changed, 46 insertions(+), 17 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c index 2518cebbf931c..0dd81b18716c3 100644 --- a/drivers/gpu/drm/i915/gt/intel_ggtt.c +++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c @@ -287,8 +287,11 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm, */ gte = (gen8_pte_t __iomem *)ggtt->gsm; - gte += vma_res->start / I915_GTT_PAGE_SIZE; - end = gte + vma_res->node_size / I915_GTT_PAGE_SIZE; + gte += (vma_res->start - vma_res->guard) / I915_GTT_PAGE_SIZE; + end = gte + vma_res->guard / I915_GTT_PAGE_SIZE; + while (gte < end) + gen8_set_pte(gte++, vm->scratch[0]->encode); + end += (vma_res->node_size + vma_res->guard) / I915_GTT_PAGE_SIZE; for_each_sgt_daddr(addr, iter, vma_res->bi.pages) gen8_set_pte(gte++, pte_encode | addr); @@ -338,9 +341,12 @@ static void gen6_ggtt_insert_entries(struct i915_address_space *vm, dma_addr_t addr; gte = (gen6_pte_t __iomem *)ggtt->gsm; - gte += vma_res->start / I915_GTT_PAGE_SIZE; - end = gte + vma_res->node_size / I915_GTT_PAGE_SIZE; + gte += (vma_res->start - vma_res->guard) / I915_GTT_PAGE_SIZE; + end = gte + vma_res->guard / I915_GTT_PAGE_SIZE; + while (gte < end) + iowrite32(vm->scratch[0]->encode, gte++); + end += (vma_res->node_size + vma_res->guard) / I915_GTT_PAGE_SIZE; for_each_sgt_daddr(addr, iter, vma_res->bi.pages) iowrite32(vm->pte_encode(addr, level, flags), gte++); GEM_BUG_ON(gte > end); diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h index 8c2f57eb5ddaa..2434197830523 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.h +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h @@ -44,7 +44,8 @@ int i915_gem_gtt_insert(struct i915_address_space *vm, #define PIN_HIGH BIT_ULL(5) #define PIN_OFFSET_BIASBIT_ULL(6) #define PIN_OFFSET_FIXED BIT_ULL(7) -#define PIN_VALIDATE BIT_ULL(8) /* validate placement only, no need to call unpin() */ +#define PIN_OFFSET_GUARD BIT_ULL(8) +#define PIN_VALIDATE BIT_ULL(9) /* validate placement only, no need to call unpin() */ #define PIN_GLOBAL BIT_ULL(10) /* I915_VMA_GLOBAL_BIND */ #define PIN_USER BIT_ULL(11) /* I915_VMA_LOCAL_BIND */ diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index 2be43885a2b5d..ff24a654565f6 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -417,7 +417,7 @@ i915_vma_resource_init_from_vma(struct i915_vma_resource *vma_res, obj->mm.rsgt, i915_gem_object_is_readonly(obj), i915_gem_object_is_lmem(obj), obj->mm.region, vma->ops, vma->private, __i915_vma_offset(vma), -
[PATCH 2/3] drm/i915: Introduce guard pages to i915_vma
From: Chris Wilson
Introduce the concept of padding the i915_vma with guard pages before
and after. The major consequence is that all ordinary uses of i915_vma
must use i915_vma_offset/i915_vma_size and not i915_vma.node.start/size
directly, as the drm_mm_node will include the guard pages that surround
our object.
The biggest connundrum is how exactly to mix requesting a fixed address
with guard pages, particularly through the existing uABI. The user does
not know about guard pages, so such must be transparent to the user, and
so the execobj.offset must be that of the object itself excluding the
guard. So a PIN_OFFSET_FIXED must then be exclusive of the guard pages.
The caveat is that some placements will be impossible with guard pages,
as wrap arounds need to be avoided, and the vma itself will require a
larger node. We must not report EINVAL but ENOSPC as these are unavailable
locations within the GTT rather than conflicting user requirements.
In the next patch, we start using guard pages for scanout objects. While
these are limited to GGTT vma, on a few platforms these vma (or at least
an alias of the vma) is shared with userspace, so we may leak the
existence of such guards if we are not careful to ensure that the
execobj.offset is transparent and excludes the guards. (On such platforms
like ivb, without full-ppgtt, userspace has to use relocations so the
presence of more untouchable regions within its GTT such be of no further
issue.)
Signed-off-by: Chris Wilson
Cc: Matthew Auld
Reviewed-by: Matthew Auld
Signed-off-by: Tvrtko Ursulin
Signed-off-by: Andi Shyti
---
drivers/gpu/drm/i915/gt/intel_ggtt.c | 12 ++--
drivers/gpu/drm/i915/i915_gem_gtt.h | 1 +
drivers/gpu/drm/i915/i915_vma.c | 28 ++-
drivers/gpu/drm/i915/i915_vma.h | 5 +++--
drivers/gpu/drm/i915/i915_vma_types.h | 3 ++-
5 files changed, 39 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c
b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 6549b8e3adbfc..717135f5bf5a6 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -266,8 +266,12 @@ static void gen8_ggtt_insert_entries(struct
i915_address_space *vm,
gte = (gen8_pte_t __iomem *)ggtt->gsm;
gte += vma->node.start / I915_GTT_PAGE_SIZE;
- end = gte + vma->node.size / I915_GTT_PAGE_SIZE;
+ end = gte + vma->guard / I915_GTT_PAGE_SIZE;
+ while (gte < end)
+ gen8_set_pte(gte++, vm->scratch[0]->encode);
+
+ end += (vma->node.size - vma->guard) / I915_GTT_PAGE_SIZE;
for_each_sgt_daddr(addr, iter, vma->pages)
gen8_set_pte(gte++, pte_encode | addr);
GEM_BUG_ON(gte > end);
@@ -317,8 +321,12 @@ static void gen6_ggtt_insert_entries(struct
i915_address_space *vm,
gte = (gen6_pte_t __iomem *)ggtt->gsm;
gte += vma->node.start / I915_GTT_PAGE_SIZE;
- end = gte + vma->node.size / I915_GTT_PAGE_SIZE;
+ end = gte + vma->guard / I915_GTT_PAGE_SIZE;
+ while (gte < end)
+ gen8_set_pte(gte++, vm->scratch[0]->encode);
+
+ end += (vma->node.size - vma->guard) / I915_GTT_PAGE_SIZE;
for_each_sgt_daddr(addr, iter, vma->pages)
iowrite32(vm->pte_encode(addr, level, flags), gte++);
GEM_BUG_ON(gte > end);
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h
b/drivers/gpu/drm/i915/i915_gem_gtt.h
index c9b0ee5e1d237..f3ae9afdee158 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -41,6 +41,7 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
#define PIN_HIGH BIT_ULL(5)
#define PIN_OFFSET_BIASBIT_ULL(6)
#define PIN_OFFSET_FIXED BIT_ULL(7)
+#define PIN_OFFSET_GUARD BIT_ULL(8)
#define PIN_GLOBAL BIT_ULL(10) /* I915_VMA_GLOBAL_BIND */
#define PIN_USER BIT_ULL(11) /* I915_VMA_LOCAL_BIND */
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 4b4a6dcdc676b..bf0f8d7e13405 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -633,7 +633,7 @@ bool i915_gem_valid_gtt_space(struct i915_vma *vma,
unsigned long color)
static int
i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
{
- unsigned long color;
+ unsigned long color, guard;
u64 start, end;
int ret;
@@ -641,7 +641,7 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64
alignment, u64 flags)
GEM_BUG_ON(drm_mm_node_allocated(&vma->node));
size = max(size, vma->size);
- alignment = max(alignment, vma->display_alignment);
+ alignment = max_t(typeof(alignment), alignment, vma->display_alignment);
if (flags & PIN_MAPPABLE) {
size = max_t(typeof(size), size, vma->fence_size);
alignment = max_t(typeof(alignment),
@@ -652,6 +652,9 @@ i915_vma_insert(struct i915_vma *vm
